Fischer, a rancher and little-known state lawmaker, maintained a positive, above-the-fray tone while Bruning and state Treasurer Don Stenberg consistently traded blistering barbs. But she also benefited from a flurry of outside spending against Bruning, the front-running establishment favorite for more than a year who watched his polling lead evaporate during the final week of the campaign.

The victory sends Fischer to the general election as a favorite over former Sen. Bob Kerrey, who easily disposed of four lesser-known opponents for a shot at the open seat being left vacant by retiring Sen. Ben Nelson. Nebraska is a must-win for Republicans if they are to acquire the four pickups necessary to flip control of the Senate this fall.

Democrats argued that Fischer’s surprising win provides with them a better chance at holding the seat, mainly because she’s largely untested and undefined. But public polling taken ahead of the primary has shown Fischer defeating Kerrey by double digits. Republicans outnumber Democrats by about 170,000 and presumptive nominee Mitt Romney is expected to rout President Barack Obama in the state.